1. Field of the Invention
The invention relates to a detecting device, a method for manufacturing the detecting device, and an electronic apparatus using the detecting device.
2. Description of Related Art
Conventionally, a detecting device using a piezo-electric element has been known for detecting acceleration. Such devices have been incorporated in small-sized portable equipment such as a wristwatch or the like.
For example, a conventional detecting device comprises a piezo-electric element attached to a circuit supporter in a wristwatch case, and a weight mounted to the surface of the piezo-electric element. In such a device, when an acceleration is given to the weight by suddenly moving the wristwatch case from the piezo-electric element side to the weight side or from the weight side to the piezo-electric element side, and by suddenly stopping the movement, the piezo-electric element is compressed by the energy of the weight to generate a voltage in the piezo-electric element, and the generated voltage is detected as a detection signal.
Another conventional detecting device comprises a piezo-electric element arranged at a lower end position in a containing chamber which is formed in a watch case, a magnet arranged at an upper position in the containing chamber, and a movable body which is attracted by the magnet and can also move in the containing chamber. In such a device, when an acceleration is given to the movable body by suddenly moving the wristwatch case upward or downward and by suddenly stopping the movement, the movable body is moved downward against the magnetic force of the magnet to contact and compress piezo-electric element, thereby causing the piezo-electric element to generate a voltage which is detected as a detection signal.
However, according to the above described conventional detecting devices, because a structure is required for generating a voltage by applying a pressure to the piezo-electric element, only one of accelerations in the upward and downward (vertical) direction and in the right and left (horizontal) direction can be detected. In such detecting devices, moreover, a control circuit is required for reforming the waveform of voltage supplied from the piezo-electric element, and the complexity and production cost are thus increased. Further, there is a problem in that the whole device requires a large size because a weight or a movable body having a large mass is required to sufficiently detect the waveform of the voltage supplied from the piezo-electric element.
Still further, in a conventional acceleration sensor, a conductive ball is ordinarily lifted up by the magnetic force of a magnet and is held at the upper limit position spaced upward from a pair of electrode pins. When the acceleration sensor is moved downward and thereafter suddenly stopped, or the acceleration sensor is moved upward suddenly, that is, when an upward acceleration is applied to the acceleration sensor, the conductive ball is moved downward to bring into contact with a pair of electrode pins against the magnetic force of the magnet by the inertial force thereof. Thereby, the pair of electrode pins are electrically connected with each other through the conductive ball to output an acceleration detection signal.
In order to manufacture an acceleration sensor having such a structure, generally, a magnet which was previously magnetized, and a conductive ball are put in an upper containing chamber and a lower containing chamber, of a part of a housing, respectively. When the part of the housing is combined with another part of the housing, the conductive ball is often sprung out of the lower containing chamber of the part of the housing by the magnetic attraction force of the magnet. In order to overcome this problem, a magnetic material which was not magnetized, and a conductive ball are put in an upper containing chamber and a lower containing chamber, of a part of a housing, respectively, and the part of the housing is combined with another part of the housing while a pair of electrode pins are incorporated in the device, and thereafter the magnetic material is magnetized by magnetizing the whole acceleration sensor.
In such a conventional acceleration sensor, because not only the magnet but also the conductive ball and the electrode pins are magnetized, it is preferable to carry out demagnetization for the conductive ball and the electrode pins. However, although it is possible to demagnetize the electrode pins but, it is not possible to demagnetize the conductive ball because the conductive ball can freely move in the lower containing chamber of the housing. Accordingly, there is a problem in that it is impossible to detect a delicate acceleration because the detection sensitivity depends on the traveling position of the conductive ball.
Further, there is another problem in that adjustment of the detection sensitivity cannot be easily performed because the magnet is contained in the blocked upper containing chamber.